1. Field of the Invention
The present invention relates to a multi-point spot welding machine controller.
2. Description of the Prior Art
Spot welding machines are commonly used in mechanical manufacturing industry. Normally, two workpieces, such as two zinc-plated steel sheets, are connected by a spot welding procedure comprising the following steps: firstly, clamping the two workpieces by two electrodes; secondly, applying electrical power through the two electrodes resulting in a low voltage and high current to pass through two welding points of the two workpieces; thirdly, stopping applying electrical power to the electrodes yet retaining the two electrodes to clamp the two workpieces for a specific time period; fourthly, releasing the two electrodes from the two workpieces. For multi-point spot welding, a working person has to repeat the above procedure from one welding point to another welding point thus wasting time. Several multi-point spot welding machines are commercially available, yet while these machines provide synchronous welding to a number of welding points at the same time, they also consume a great deal of electricity in a short time period. These machines can not operate properly in a working site where the electricity supply is not great enough. Moreover, the great amount of electricity applied on the workpiece will cause high temperature thereon and damage the outer surface of the zinc-plated steel sheet thus resulting in zinc molecules forming a zinc film to cover the electrodes. In this situation the conductivity of the electrodes is decreased and lowers the welding effect of the welding machine. It is requisite to provide a multi-point spot welding controller to synchronously/asynchronously control a multi-point spot welding machine to connect two workpieces without resulting in the above problems.